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Health, Science, Environment

Zika-carrying mosquitoes don’t live in St. Louis, but health departments are making plans

A female Aedes aegypti mosquito feasts on the blood of CDC photographer James Gathany. Aedes aegypti is the type of mosquito most likely to carry Zika and other tropical diseases.
James Gathany | Centers for Disease Control and Prevention
A female Aedes aegypti mosquito feasts on the blood of CDC photographer James Gathany. Aedes aegypti is the type of mosquito most likely to carry Zika and other tropical diseases.

The breed of mosquito most likely to carry the Zika virus probably won’t make its way to St. Louis this summer, but local public health agencies are still taking precautions.

This type of mosquito typically lives in tropical climates, so it doesn't thrive in the St. Louis region. But as the weather warms, mosquitoes expand their range. 

"It was a very mild winter in most of the southern U.S.," said Sarah Patrick, deputy director for the St. Louis County Department of Public Health. "We just want to be prepared."

Cases transmitted by local mosquitoes have not yet occurred in the continental U.S., but the Centers for Disease Control and Prevention has confirmed at least 349 in Puerto Rico, American Samoa and the U.S. Virgin Islands.

Only one in five patients who catch Zika will show mild symptoms. But when passed from a pregnant woman to a developing fetus, the virus has been linked to a condition called microcephaly, in which babies are born with small heads and brain damage. Zika can also be transmitted sexually.

Last week, the state health department reported that a pregnant Missouri woman who had traveled to Honduras later tested positive for the Zika virus. 

In St. Louis, public health agencies have turned their attention to reducing local mosquito populations before the season begins. Patrick’s department has begun using larvicide where local mosquitoes are known to lay eggs.  Though the agency uses a mosquito trap designed to catch the bugs that carry the deadly West Nile virus, the mosquitoes that carry Zika are different, and Patrick said she hopes to purchase additional traps.

In the meantime, she is asking residents to clean up their own yards and garages to reduce the presence of standing water, which mosquitoes use to breed.

“Look for things like trash that could have small amounts of water gathered in them, overturned flowerpots that have standing water, tires,” Patrick said. “Right now is a great time to take an inventory of your surroundings to find those pools of water.”

Dr. Thomas Zink, who serves as medical advisor for the city of St. Louis, recommends the same. He points to maps from the Centers for Disease Control and Prevention, which show that the type of mosquito most likely to carry the Zika virus is not typically identified in Eastern Missouri.  

Maps from the Centers for Disease Control and Prevention show the agency's best estimate for the potential range of two mosquito species; the type mapped on the left is more likely to spread Zika than the one on the right. Maps are not meant to represent
Centers for Disease Control and Prevention

“The Zika virus can be flown in, can come up through river travel, can get into cars and come into our area. But even still, for some reason it can’t get a foothold just yet,” Zink said.

President Barack Obama has asked Congress to appropriate $1.9 billion to prevent the spread of Zika both domestically and abroad.

The CDC has issued travel alerts for pregnant women going to South American and Central American countries, as well as the Caribbean, Pacific Islands, Cape Verde and Mexico. The agency has drawn up guidelines to prevent sexual transmission of the virus, including that men who travel to areas with Zika use condoms or abstain from sex for at least two months, even if they did not develop symptoms.

Follow Durrie on Twitter: @durrieB.

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